Macs don't support recording to USB drives. They all have a firewire port so a good firewire drive will be needed(OWC are a good choice), OR you can swap the optical drive for a second internal drive if you're game(youtube.com has videos showing how). There are also some thunderbolt drives on the market and that should also work fine. I highly recommend an i7 quad core, no matter which iMac or MBP you are considering. The horsepower is excellent(and you can't have too much power)
